An aorta valve usually consists of three cusps and is located at the exit of a left ventricle that sends blood to the entire body. The back flow of blood is prevented by opening and closing the valve. However, the valve may harden due to various causes, including congenital problems, aging, arterial sclerosis, rheumatism, and so on, making it difficult for a hardened valve to move freely. When the valves cannot move freely, the area where blood can pass becomes narrower, adversely affecting the blood flow from the left ventricle to the aorta. This symptom is called aortic stenosis.
Severe aortic stenosis causes calcification and adhesion. Major treatments for aortic stenosis are medication and surgical operations. The main surgical operations are aortic valve replacement with a mechanical or bioprosthetic valve. For a patient who cannot take a risk of open heart surgery because of their age or other reasons, transcatheter aortic valve replacement (TAVR) with an artificial valve may be performed.
It is expected that transcatheter aortic valve replacement (TAVR) will be used as a treatment for aortic stenosis. Transcatheter aortic valve replacement (TAVR) is a surgical procedure including a process of inserting a catheter from the femoral artery to the apex of the left ventricle and placing an artificial valve near the aorta valve via the catheter. When planning the treatment, a diameter of a vessel, an area of an aorta valve, and a status of calcification are checked using a computed tomography (CT) image, and a length and a path of a catheter, and a size of an artificial valve are determined based on the check result. For example, there is a known technique of searching for a luminance of a heart valve at each of a contract cycle and an expansion cycle in the direction of a vessel core to calculate an opening and closing region of the heart valve, and expressing the level of opening and closing of the heart valve in different colors.
To attach an artificial valve near the aortic valve securely, it is desirable if there is a certain amount of calcium around the root of the aortic valve and no calcium at the tip of the aortic valve. However, no conventional techniques have provided a means of checking such conditions. With a conventional technique, a length and a thickness of a catheter, a width of a path for the catheter, and a size of an artificial valve were determined only based on a diameter of a femoral artery or an aorta that is a path of the catheter, a calcification status, or an area of an aortic valve. Moreover, it was impossible to evaluate the degree of ease or difficulty of implanting an artificial valve based on objective observance of calcium distribution near an aortic valve.
Various forms of an artificial valve greatly affect the degree of ease or difficulty of implanting an artificial valve. Thus, the level of ease or difficulty of attaching an artificial valve is dependent on the degree of sedimentation of calcification of a part where the artificial valve touches a blood vessel. If the amount of calcium is greater or less than an expected amount, it is necessary to reconsider the placement position, the size, and the form of the valve. Not only the conditions of an aortic valve, but also the evaluation of calcification in the vessel wall are important elements. A technique of evaluating these elements integrally and objectively is not known.